1. Field of the Invention
The present invention relates to a liquid crystal display device and a method of manufacturing a liquid crystal display device, and more particularly to adjustment of a liquid crystal injection port in a process of manufacturing the liquid crystal display device.
2. Description of the Background Art
Heretofore, in a liquid crystal display device, electrodes are formed, liquid crystal is sealed between insulating substrates arranged to be opposed to each other by a seal material, and liquid crystal molecules are aligned in a predetermined direction by utilizing an alignment film formed on the electrodes.
A signal voltage driving the liquid crystal is applied between the electrodes formed on the insulating substrate, thereby controlling alignment of the liquid crystal for displaying.
The seal material sealing the liquid crystal includes a seal periphery formed in a rectangle to surround the liquid crystal, and seal extending portions extending from the seal periphery to an end surface of a liquid crystal display panel. The seal extending portions form an injection port for injecting the liquid crystal between the insulating substrates. The injection port is sealed by a sealing material after the liquid crystal is injected between the insulating substrates.
Liquid crystal display devices having gate line driving circuits built-in, which are configured by amorphous silicon thin film transistors (hereinafter referred to a-Si TFTs: amorphous thin film transistors), are employed for screens of notebook computers, personal digital assistants (PDAs), portable multimedia players (PMPs), personal navigation devices (PNDs), for example, which are easy to have large areas and have high productivity (see Jin Young Choi, Jin Jeon, Jong Heon Han, Seob Shin, Se Chun Oh, Jun Ho Song, Kee Han Uh, and Hyung Guel Kim, “A Compact and Cost-efficient TFT-LCD through the Triple-Gate Pixel Structure”, pp 274 to pp 276, SID '06 DIGEST).
In the gate line driving circuit, an area where wiring patterns having different potential intersect exists in order to configure a circuit.
Here, a frame of the liquid crystal display panel is narrowed, namely, at least a part of the gate line driving circuit needs to be arranged below the seal periphery surrounding the liquid crystal display panel in order to reduce an area where liquid crystal display is not performed.
Although seal-inside spacers such as microrods and silica spheres are generally mixed into the seal material in order to form a gap of a liquid crystal cell, in a case where the gate line driving circuit is arranged below the seal periphery mixed with the seal-inside spacers, the circuit pattern is pressed and broken by the seal-inside spacers, and an electric short-circuit occurs. Particularly, when a soft metal wire such as Al is employed as the gate line driving circuit, this phenomenon is prominent.
Therefore, it is impossible to arrange the gate line driving circuit below the seal material in this situation. However, as this measure, there is a method of using only column spacers (gap holders) forming the gap of the liquid crystal cell without the seal-inside spacers such as microrods and silica spheres.
However, even when the cell gap is formed by only the column spacers without the seal-inside spacers, there are problems as follows.
In a general method of manufacturing a liquid crystal display device, a color filter substrate formed with color filters, and an array substrate formed with transistor devices, capacitative elements, electrode wires and the like are prepared, and pasted together to assemble a liquid crystal cell. Thereafter, the liquid crystal cell is cut into a predetermined size, and liquid crystal is injected into the liquid crystal cell.
This liquid crystal injection process employs a vacuum injection method, in which an empty liquid crystal cell is evacuated in a vacuum container, an injection port of the evacuated empty liquid crystal cell is then immersed in a liquid crystal material, an area therearound is thereafter returned to ordinary pressure, and the liquid crystal material is injected into the liquid crystal cell.
In a case where the cell gap of the liquid crystal cell is formed by only the column spacers, even when the cell gap can be successfully formed without narrowing the injection port in panel pasting, there is a problem of increasing evacuation time due to the following reason.
In the vacuum injection method, after the liquid crystal cell is prepared in the vacuum container, and the vacuum container is evacuated by a vacuum pump to become a vacuum state, an injection port side of the liquid crystal cell is immersed at several millimeters in the liquid crystal material.
Next, the vacuum container in the vacuum state is gradually returned to atmospheric pressure by leak, and the liquid crystal material is injected into the liquid crystal cell from the injection port by action of pressure difference between atmospheric pressure and air pressure in the liquid crystal cell, and action of capillarity of the liquid crystal.
At the time of completing injection of the liquid crystal material, a sealing material is applied to the injection port, and the sealing material is subjected to ultraviolet curing or thermal oxidation, thereby sealing the injection port.
When evacuating to become a vacuum state, a vacuum degree of inside of the vacuum container is more rapidly increased than that of the empty liquid crystal cell. Consequently, a thickness of a center of the liquid crystal panel greatly increases compared to that at ordinary pressure. At this time, stress employing the seal periphery as a supporting point is applied to the whole liquid crystal panel, and consequently, the injection port narrows. There is a problem that evacuation time increases when the liquid crystal material is injected from the narrowed injection port.
When the inside of the vacuum container is returned to ordinary pressure, and the liquid crystal material is injected inside the liquid crystal panel in a state where the injection port is immersed in the liquid crystal material, the inside of the vacuum container is more rapidly returned to ordinary pressure than the inside of the liquid crystal panel, and the thickness of the center of the liquid crystal panel reduces. Consequently, the injection port is widened, and injection time of the liquid crystal material does not increase.